2D layered materials: structures, synthesis, and electrocatalytic applications

The discovery of graphene has opened a new world of 2D materials with abundant components and diverse bonding modes that have strong covalent bonds in a plane but weak interactions out of the plane. One of the many alluring features of two-dimensional materials is that they can be exfoliated in liquids. This peculiarity makes them able to be exfoliated into thin nanosheets with few layers or even monolayers. Exfoliation endows nanosheets with unique laterally extended topology, novel mechanical performance, and highly exposed surface, which are ideal for catalysis that mainly occurs on the material surface. In addition, the exfoliated nanosheets show unprecedented optical and electrical properties owing to the two-dimensional confinement of electrons. The unique electronic structure and surface structure of layered materials have attracted tremendous research interests in catalysis and energy conversion fields. This review first introduces the history of the development of layered materials and summarizes the structural chemistry based on connection modes of laminates and types of intercalation ions. Furthermore, rational methods are elaborated to achieve controllable exfoliation of different kinds of layered materials, with emphasis on the exfoliation mechanism and application sphere of each method. Furthermore, we discuss the latest research progress of layered materials as electrocatalysts and electrocatalyst support for application in energy conversion and highlight the relationship between catalytic performance and the layered structure based on theoretical and experimental results. Finally, we also explore the future prospects of 2D layered materials in the field of electrocatalysis, such as water splitting, CO 2 reduction, and N 2 fixation. At the same time, constructive suggestions on chemical synthesis, extended application, and improvement in structure stability are also proposed. We review the synthesis, structure and electrochemical applications of 2D nanomaterials, with particular emphasis on the relationship between their structure and catalytic activity.